The present invention relates to an injection molding machine for producing different parts that has a linkage for producing unequal strokes during the opening and closing of the mold sections. The present invention also relates to a method for fabricating molded articles of different sizes using a single molding machine.
A multi-level stack mold typically uses a linkage system to open and close the mold sections while maintaining equal spacing between all sections.
U.S. Pat. No. 3,669,601 to Lainesse shows an early two level stack mold which is opened by the motion of a platen. As the platen moves, a first mold station nearest the platen opens, while a second mold station remains closed. Pins, fastened to a center section, slide through a pair of plates until their heads contact the underside of one of the plates, thus limiting the opening stroke of the first mold station. As the platen continues to move, the center section is now caused to move via the pins. Other pins, fastened to the center section, slide through a second pair of plates until their heads contact the underside of an ejector plate causing it to move and compress springs which cause the second mold station to open. Motion of the platen continues until the heads, already bottomed out on the ejector plate, fully compress the springs thereby ejecting the parts from the second mold station. This mechanical system thereby causes a two level stack mold to open sequentially, first one side, then the other.
U.S. Pat. No. 3,941,548 to Bruder shows a two level stack mold which uses pairs of cylinders hydraulically connected to each other such that the opening motion of a movable platen causes an upper rod of an upper cylinder to move inside the cylinder and displace oil that is conducted via a pipe to a lower cylinder acting on its piston and causing a lower rod to extend and push against a fixed platen, thereby causing the center section of the stack mold to separate from the fixed platen. In this way, both mold stations are opened simultaneously by equal amounts at equal speeds.
U.S. Pat. No. 4,400,341 to Sorensen shows a two level stack mold in which a center section is opened independently of the moving platen by means of a cylinder. Each mold station is opened sequentially according to the stroke of the cylinder. One mold is opened while the others remains closed.
U.S. Pat. No. 4,207,051 to Wright shows a two level stack mold in which pairs of racks acting with a central pinion cause the mold stations to open simultaneously and equally in both stroke and speed.
U.S. Pat. No. 4,929,166 to DiSimone shows a two level stack mold carrier in which machine mounted castings for holding the center section of a stack mold are moved by means of pairs of racks and pinions having different diameters, and both mounted on the moving platen, such that the center section of the mold remains equally spaced between the fixed and moving platens of the machine.
U.S. Pat. No. 5,458,843 to Brown shows a four level stack mold linkage system in which all mold stations are opened equally in both stroke and speed via the opening motion of the moving platen.
U.S. Pat. Nos. 5,578,333 and 5,707,666, both to Schad, show multilevel stack mold carriers for four level stack molds in which nested castings mounted in the machine, support various sections of the stack mold and are moved by nested drive means such that the centermost section is driven first by the moving platen motion. Mounted to the center carrier are secondary drive means to cause the motions of the remaining mold sections such that all mold stations are open/closed equally both in speed and distance.
None of the above mentioned patents describe a linkage mechanism for opening and closing the various sections of a stack mold by unequal distances between the various mold sections. Nor are there any descriptions of linkage mechanisms for facilitating such unequal motions in an adjustable manner such that a stack mold carrier so equipped can be used to accommodate installations of different stack mold configurations requiring different unequal strokes.